Preparation of Mesoporous ZnO Microspheres through a Membrane-Dispersion Microstructured Reactor and a Hydrothermal Treatment

Abstract

Mesoporous ZnO microspheres with a diameter of about 10 μm were prepared through the combination of a membrane-dispersion microstructured reactor with a hydrothermal process. First, ZnSO4 reacted with NH4HCO3 in a membrane-dispersion reactor to produce the Zn5(CO3)2(OH)6 precursor, and then the precursor was treated at the temperature of 80 °C for 2 h to form the Zn5(CO3)2(OH)6 microspheres aided by the surfactant CTAB or F127; after the calcinations, mesoporous ZnO microspheres were obtained. The experimental results showed that the morphology of ZnO microspheres obtained using the membrane-dispersion microstructured reactor to mix the raw materials was better than that of those obtained using stirred tanks. Without surfactants and the hydrothermal treatment of the precursors, uniform ZnO microspheres could not be obtained. The SEM images showed that the monodispersed ZnO microspheres were assembled by the plates, and deeper observations revealed that these plates were aggregated by the ZnO nanorods formed by ZnO nanoparticles with a diameter of 9.0 nm. The adsorption–desorption isotherm curve indicated that the ZnO microspheres had mesoporous structures with an average pore diameter of 13.8 nm when using CTAB as the surfactant, and the specific surface area of the ZnO microspheres could reach 71.3 m2/g, much higher than that of ZnO nanoparticles.